The present invention relates to a mechanical fuel injection pump for injecting fuel to internal combustion engines. In, for example, Japanese Laid Open Patent Application No. 57-56660, a mechanical fuel injection pump has been proposed for determining an injected amount of fuel and an injection timing of the fuel, wherein fuel is filled on both sides of a shuttle disposed intermediately in a high pressure chamber, with the fuel on one side of the shuttle being pressurized at a predetermined time to determine the injection timing, and, at the same time, the fuel on the other side of the shuttle being pressurized to determine an injected amount of fuel.
A disadvantage of a fuel injection pump of the aforementioned type resides in the fact that, since fuel for determining the injection timing and fuel for determining the injected amount are respectively supplied to either one side of the shuttle, the fuel for determining the injected amount influences a position of the shuttle thereby resulting in a disturbing or an adverse affecting of the injection timing of the fuel.